The Possible Influences of Sudden Events on Biological Radiations and Extinctions

Abstract

This report, and the Workshop discussions leading to it, stem from the growing realization that physical events of short duration may have had frequent, significant, and lasting effects on the Earth’s biota. For the purposes of the report, physical events are considered relevant only if they are: a) relatively sudden, b) have a global or nearly global biologic effect, and c) are amenable to analysis through a combination of physical prediction and empirical observation. The time durations of the physical events themselves cannot be strictly defined, but most are short enough to be considered instantaneous on a geologic time scale. This generally means a duration of 10⁴years or less, with a definite bias toward truly instantaneous events. The geographic scale of events and their geochemical, sedimentologic, and biologic effects can be determined from theoretical models and from the geologic record; there are, however, many uncertainties attached to the theoretical predictions and the incompleteness of the geologic record prevents a full understanding both of their cause and their effects.